DE2644741A1 - FIRE-RESISTANT LINING OF STATIONARY OR MOVABLE BARRELS FOR ACCOMMODATION OF PIG IRON - Google Patents

Description

DR. ING. F. "WUESTHOFF DR. E. ν. PEOHMANN DR. ING. D. BEHRENS DIFI ,. ING. R. GOETZ PATENT LAWYERS

2.

S MUNICH SCHWEIGEHSTRASSE TELEPHONE- (089) 66 20 IXLEl 5 2 * 070

PHOTKCTPATEIiT MÜ3fCn £ 2i

1A-48 399

description

to the patent application

VEITSCHER MAGNESITWERKE-AKTIEN-GESELLSCHAFT A-1011 Vienna, Schubertring 10-12

concerning

"Refractory lining of stationary or moving vessels for holding pig iron"

709815/0881

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The invention relates to the refractory lining of _: stationary or movable vessels for holding pig iron.

As is known, the intermediate vessels for the pig iron between the blast furnace and the steel melting unit are stationary Mixers, e.g. roller mixers, or movable pans, e.g. torpedo pans, are used. These intermediate vessels are used for example for transporting the pig iron, for achieving a uniform composition of the pig iron, for interception and storage of excess pig iron, which is not immediately processed further, as well as for keeping the pig iron warm.

These vessels are usually lined with magnesite, dolomite or high alumina bricks. Since the operating temperatures in conventional vessels of this type do not exceed 14oo ° C, the wear is mainly dependent on the attack of slag. The slag consists predominantly of CaO + SiO ₂ (mostly over 60% by weight), with a CaO / SiO ^ weight ratio of about 0.6-1.4%, and mostly has a considerable alkali metal oxide content (up to 15% by weight) .

Magnesite bricks show a good match especially in stationary mixers, while dolomite bricks in transport ladles have good shelf lives. High alumina bricks are very susceptible to slag with higher CaO contents and with alkali metal oxide contents and are therefore rarely used.

Due to the development of more efficient blast furnaces with ever larger frame diameters, for reasons of Furnace guidance ever higher tapping temperatures of the pig iron in Purchase to be taken. The consequence of this is an increase in the temperatures in the subsequent intermediate vessels to values above 14oo ° C. The durability of the magnesia stones built into these vessels, mostly made of iron-rich sintered magnesia, was increased worse and in individual cases only achieved half of the throughput that was achieved before the large blast furnaces were commissioned became. The obvious improvement of magnesia stones in the direction of higher hot strength by using higher quality Low-iron sintered magnesia also did not produce a satisfactory improvement in shelf life.

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The aim of the invention is to create a lining for high-temperature mixers, that is to say those with operating temperatures above 14oo C , which provides better durability compared to the stone qualities previously used there.

According to the invention, this is achieved through the use of magnesite chromestones with a Cr ^ O ^ content of 15 to 3o wt .-%, preferably 20 to 25% by weight, the chromite used being dissolved in the stone mass to such an extent that chromite remains only in a proportion of a maximum of 12% by volume, preferably a maximum 5% by volume are present in the stone for the refractory lining of stationary or movable vessels for holding pig iron, e.g. pig iron mixers, torpedo pans or the like.

The better durability of such magnesite chrome stones is surprising, since chromite itself is caused by the in the mixer slag contained alkali metals is strongly attacked. However, this attack is far less powerful, if stones are used according to the invention in which the chromite used in the course of a manufacturing fire in the Periclase basal tiasse dissolved to the specified high extent and after cooling it is essentially only contained in the form of newly formed chromite spinels. Also angry at the attack These stones withstand slag better.

This high chromite resolution can be caused by common Melting of chrome ore and a magnesia carrier can be achieved. The solidified melt is crushed and shaped into stones.

Another type of production to be used in accordance with the invention Stone is the joint sintering of chrome ore and a magnesia carrier, such as raw magnesite, caustic burned Magnesia or sintered magnesia, without melting down, as described, for example, in OE-PS 301 433. In this case, the Chromite grains used in the course of a high-temperature fire, E.g. at temperatures above 2ooo ° C or above 21oo ° C, in the periclase base dissolved in the form of a solid solution and newly formed chromite spinels separate on cooling. That kind of thing The pre-reacted sintered material obtained is then processed into stones.

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There is also the possibility of avoiding the joint melting or the joint sintering fire and achieving the chromium dissolution in the course of the stone fire, e.g. at a temperature of 170 to 190O ⁰ C, if the chrome ore used in the stone mixture and also a proportion (e.g. up to to 10% by weight) of the sintered magnesia used are present in finely divided form below 0.1 mm, with at least 70% by weight of these fine fractions each having a grain size below 0.06 mm. In order to achieve better resistance to temperature changes, it can be advisable to provide a subordinate proportion (for example 10 to 40% by weight) of the chrome ore in a coarse grain size of 0.5 to 5 mm, preferably 0.7 to 2 mm ^. This coarse proportion is to be disregarded when determining the chromite relics, ie the microscopically detectable residual components of the originally used chromium ore grains. In this production variant, it is advisable to use 26 to 56% by weight of chrome ore in the stone mixture. When using a high-quality chrome ore with a Cr ^ CU content of 45 to 57% by weight, as is preferable for all production variants of the stones to be used according to the invention, this results in a Cr ₂ O ₃ gel of around 15 to 25% by weight. ~% in the stones.

The following example serves to illustrate the invention.

Example: "

A mixture of 41% by weight of chrome ore and 59% by weight of caustic burned magnesia was sintered to produce A magnesia chrome sintered material was produced at a temperature of 215o ° C. The starting materials and the sintering material were as follows Analysis (calculated without glow loss):

Wt% magnesia Chrome ore Sinter SiO ₂ Il o, 48 1.42 o, 82 Al ₂ O ₃ Il o, 3o 14.73 6.46 ^Fe 2 ° 3 Il 5.3o 28, oo 14.89 Cr ₂ O ₃ - It - 46.49 2o, 47 CaO Il 2.89 0.06 1.91 MgO Difference) 91, o3 9.3o 55.45 (the end Mt ^ k ** _ jk λ mm. _— j

709815/0881

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A stone mixture was made from the sintered material manufactured with the following grain structure:

3 - 5 mm 25% by weight

1 - 3 mm 35% by weight

o, l - 1 mm 2o wt .-%

ο - o, l mm 3o wt .-%

The mixture was treated with about 4% magnesium sulfate solution

sets and pressed into stones with a pressure of 125o kp / cm, which were dried and then fired in a tunnel kiln at 180 ° C. for 4 hours (stone quality A). In the course of manufacture the chrome ore components were completely dissolved in the periclase. There were no chromite relics in the finished stones contain more.

Another quality (stone quality B) was made from a sintered magnesia and a chrome ore following chemical analysis manufactured:

Sintered magnesia chrome ore

SiO ₂ o, 32 Wt% 2.8o Weight Al ₂ O ₃ o, 38 Il 13.42 Il Fe ₂ O ₃ 6.32 Il 15.17 ti CaO 1.85 Il o, 28 Il MgO (from difference) 91.13 Il 15.51 Il Cr ₂ O ₃ - 52.82 Il

During the stone production, which was carried out in the same way as for stone quality A, the following grain structure was used turned:

Sintered magnesia 1 - 3 mm 35% by weight

0.1-1 mm 2o ^H

ο - o, l mm 5 "

Chrome ore o, l - o.7 mm Io "

ο - o, l mm 3o "

709815/0881

After the stone firing, the stones contained 4% by volume of chromite residues.

Both qualities were installed in a rotary slagging furnace and there with the usual mixer stones (stone quality C) made of iron-rich sintered magnesia compared with the following analysis.

Stone quality C SiO ₂ 0.38% by weight Al ₂ O ₃ o, 42 " Fe ₂ O ₃ 6.48 " CaO 1.76 ^ll MgQ (from difference) 9o, 96 "

Mixer slag was added to the furnace with the following analysis given up:

SiO ₂ 39.7 Wt% Fe ₂ O ₃ 12.9 Il Al ₂ O ₃ 3.1 Il CaO. 31.8 Il MgO (from difference) 2.4 Il MnO 4, ο Il Alkalis 6.1 Il

The oven was heated to a temperature of 144 ° C. and at this temperature with a rotary movement of 20 rpm Held for 3 hours and 20 minutes. After the test stones had cooled down and removed, it was found that the two according to the invention Grades A and B showed a stone removal of 0.3 and 0.4 mm, respectively, while the comparison stone quality C showed 9 mm wear was.

In a 15oo t mixer lined with quality C. • In the main area of wear and tear, a test field was set up, consisting of both grades A and B, half. built-in. After a The test stones stood for a throughput of around 52o, ooo t of pig iron A "and B are about 5a mm in front of the remaining stones C.

709815/0881 " ⁷ ~

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A 1500 t mixer was delivered with quality A and achieved a shelf life of 1.15o, ooo t throughput; against it achieved quality C during the previous kiln journeys only on average 65o, ooo t throughput.

- claim -

709815/0881

Claims (1)

Claim Use of magnesite chrome bricks with a ^
? halt of 15 to 30 wt .- 6, preferably 20 to 25 wt .- ö, wherein the chromite used is dissolved in the rock mass to such an extent that Chromitrelikte only in a proportion of up to 12 VoI ₀ -?%, preferably maximum 5% by volume, im
Stone are present for the refractory lining of
stationary or movable vessels for holding pig iron, for example pig iron mixers, pans or the like. 8183 709815/0881